The invention relates to a constant velocity joint in the form of a twin-ball joint. Such joints have the following characteristics: an outer joint part which comprises a first longitudinal axis L12 as well as an attaching end and an aperture end positioned axially opposite one another, and which comprises outer ball tracks (22); an inner joint part which comprises a second longitudinal axis L13 and attaching means for a shaft pointing towards the aperture end of the outer joint part, and which comprises inner ball tracks; the outer ball tracks and the inner ball tracks form pairs of tracks with one another which each accommodate balls; circumferentially adjoining pairs of tracks comprise center lines of the outer and inner ball tracks which, when the longitudinal axes L12, L13 are aligned, are positioned in planes E, E′ which extend parallel relative to one another and are symmetric relative to the longitudinal axes; and a ball cage positioned between the outer joint part and the inner joint part and comprising circumferentially distributed cage windows which each accommodate pairs of balls of adjoining pairs of tracks positioned in parallel planes.
When assembling fixed joints it is common practice first to insert the outer joint part, the ball cage and the inner joint part into one another and then the balls while over-articulating the joint so to speak, i.e. articulating the inner joint part and outer joint part relative to one another in such a way that each cage window of the cage guided on to half the articulation angle between the inner joint part and the outer joint part emerges from the outer joint part. Such over-articulation results in that those balls which have already been mounted and which are not positioned in the articulation plane nor in a plane extending through the ball cage axis which plane is positioned perpendicularly relative to the articulation plane are displaced in the circumferential direction of their cage windows. The greater the angle of articulation, the greater the circumferential length of the respective cage windows has to be. Lengthening the cage windows results in a reduction in the width of the webs between the cage windows. This, in turn, results in a reduction in the strength of the cage, which is undesirable.
For a constant velocity fixed joint whose pairs of tracks are positioned in radial planes and widen jointly towards the aperture of the outer joint part, it is known from U.S. Pat. No. 5,509,856 to propose a cage which comprises cage windows positioned opposite one another in a radial plane and having a first smaller circumferential length as well as cage windows whose centres are positioned outside said radial plane and a plane extending perpendicularly relative thereto and which comprise a second greater circumferential length.